Prior charged particle beam emittance measuring devices make use of collimators and screens which are cumbersome and expensive. These devices generally are large and non-portable restricting measurements to fixed beamline locations; suffer from electron permeability for high energy beams restricting their usefulness because of material and construction limitations; use phosphor screens limiting the time response of the measurement; and have poor resolution limiting use to large diameter beams. Other techniques such as wire scanners must be placed at multiple stations along the beam line and require successive scanning to determine beam profiles. While wire scanners offer better resolution, they also have limitations. Because successive scanning is necessary, wire scanners are not capable of real time measurements. Beam imaging devices and/or wire scanners have been combined with focusing magnets, which require successive beam profile scans as a function of magnet strength, and thus are not capable of real time measurement. Multiple, non-interactive wall current monitors have been disposed along beam paths, but these devices require elaborate mathematical analyses to provide emittance value. All such multi-positioned devices and measurements are sensitive to errors caused by motion and instability of the particle beam centroid. Further, all prior methods require detailed knowledge of particle trajectories and profiles in order to compute emittance. No prior art method can be used to make time resolved measurements of beam emittance at any location in a particle beam accelerator.